If the 5th day of a particular month is Wednesday, then what day will the 23rd day be?

Find the total count of days lying between the 5th and the 23rd:
$$\text{Difference}=23-5=18\text{ days}$$

Now divide by $7$ to isolate the odd days remainder value:

$$\frac{18}{7}=2\text{ weeks with a remainder of }4\text{ odd days}$$

Advance $4\text{days}$ forward from Wednesday:

* Day 1: Thursday
* Day 2: Friday
* Day 3: Saturday
* Day 4: Sunday

Therefore, the 23rd day of the month is a Sunday.